Spatial and temporal distribution characteristics of soil water in different reforestation lands of slope positions in hilly area of Southern Ningxia: A case study of Luotuolin Watershed
In order to investigate the spatial-temporal distribution of soil water in the reforestation hilly area of different slope positions in Southern Ningxia, the seasonal dynamics and vertical changes of soil water content in 0-100 cm soil layer at upper, middle, and lower slope positions of two typical slopes with natural forest of sea-buckthorn and artificial forest of pinus tabulaeformis were studied by in-situ field sampling and laboratory experiments. The results showed that the slope position with the highest soil water content was consistent with the slope position with the most favorable soil bulk density and pore conditions, which happened at the middle slope position of sea-buckthorn forest and the lower of pinus tabulaeformis forest. The slope position influenced the soil water content of natural sea-buckthorn forest below 20 cm soil depth，and below 40 cm to pinus tabulaeformis. Soil water content increased with the increase of rainfall, and the effect of rainfall on the soil water of natural forest was greater than that of artificial forest. Under the same rainfall condition, soil water content of natural sea-buckthorn forest increased more than that of artificial pinus tabulaeformis forest. The significant difference of soil water between slope positions occurred under 20 cm soil depth for natural sea-buckthorn forest, and under 40 cm soil depth for artificial pinus tabulaeformis forest. When the monthly rainfall exceeded 200 mm, the difference of soil moisture among slop positions reduced for natural sea-buckthorn forest but increased for artificial pinus tabulaeformis forest, which indicated that vegetation type had an important influence on the distribution of soil moisture content.